1. Field of the Invention
The present invention relates to a novel photoelectric conversion sensor used in an apparatus for measuring particle size or size distribution of powder and liquid spray and, more particularly, to a photoelectric conversion sensor used in an apparatus for measuring particle size or size distribution of powder and liquid spray based on the intensity distribution of scattered light obtained by radiating a collimated monochromatic light beam onto a group of particles.
2. Description of the Prior Art
Particles in a collimated monochromatic light beam exhibit scattered intensity patterns corresponding to their diameters. By measuring the scattered intensity pattern generated by a single particle or a group of particles, the particle size or the size distribution of the particles can be determined. The scattered light intensity pattern is symmetrical about the optical axis, and can be detected using a sensor consisting of concentric annular photoelectric conversion elements having their center on the optical axis. The spread of the pattern decreases with the increase of particle size. For this reason, the width of the inner elements should be smaller than the outer elements.
The gaps for insulating adjacent elements in this kind of sensor should be reduced as small as possible from the viewpoints of the precision and the resolving power in particle size measurement. However, in order to improve productivity and to minimize crosstalk between the elements, gaps larger than 10 .mu.m are preferable. Then, near the center, the width of the gaps is comparable with the width of the elements. This situation deteriorates the precision and the resolving power. Furthermore, in order to improve the response of sensors, conductive electrodes made of gold, aluminum or the like must be connected to the inner or outer edge portions or inside the elements. However, such portions do not detect scattered light. Therefore, they are another cause for deterioration of the precision and the resolving power in particle size measurement.